Attenuating devices for bumpers have taken a wide variety of different forms. Some such devices have involved piston cylinder arrangements using flowable liquids. Other devices have included collapsible members and resilient members which collapse upon impact and then restore to their original shapes after the impact, absorbing slight energy during such collapsing.
In recent years, much emphasis has been placed on the development of bumpers capable of withstanding a five mile per hour impact without damaging the vehicle or object it is protecting. In the main, devices to accomplish this have been relatively heavy and expensive to manufacture or otherwise, unsuitable for mass production.
A patent application for a bumper spring U.S. Ser. No. 766,462 filed by Epel and Wilkinson discloses a solid bumper spring which is effective in deforming under impact force and restoring to its original shape when the impact forces are removed, but the effectiveness in absorbing the impact forces is reduced by each impact. An object of the present invention is to provide an energy attenuator for repeatedly absorbing impact forces over a defined deflection distance with a relatively constant absorption efficiency.
A patent to Roubinet U.S. Pat. No. 3,999,793 discloses an energy absorbing bumper formed by a winding operation of glass filament impregnated with polymerizable resin about a core, polymerizing the resin, and then cutting the loop into two pieces to form two bumpers. The bumpers formed from this method would be substantially solid beams. Another object of this invention is to improve the bumper of Roubinet by providing films of high temperature resistant thermoplastic materials between thin layers of aligned filaments supported in a suitable matrix, thus reducing interlamellar shear problems encountered in solid bumpers.